function chooseURLJump(ob,max,url_stub,message,num_pages)
{
   var res=window.prompt(message,num_pages);
   if (res)
   {
      res=parseInt(res);
      if ((res>=1) && (res<=num_pages))
      {
         ob.href=url_stub+'&start='+(max*(res-1));
         return true;
      }
   }
   return false;
}